Add v8::Promise::Then.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index ca552fc60f6ba44140461666f730411a92de0fe4..b12534f91f55e2c92bd0af1da898f7440c93a0d6 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -5910,6 +5910,26 @@ Local<Promise> Promise::Catch(Handle<Function> handler) {
 }
 
 
+Local<Promise> Promise::Then(Handle<Function> handler) {
+  i::Handle<i::JSObject> promise = Utils::OpenHandle(this);
+  i::Isolate* isolate = promise->GetIsolate();
+  LOG_API(isolate, "Promise::Then");
+  ENTER_V8(isolate);
+  EXCEPTION_PREAMBLE(isolate);
+  i::Handle<i::Object> argv[] = { Utils::OpenHandle(*handler) };
+  i::Handle<i::Object> result;
+  has_pending_exception = !i::Execution::Call(
+      isolate,
+      handle(isolate->context()->global_object()->native_context()->
+             promise_then()),
+      promise,
+      ARRAY_SIZE(argv), argv,
+      false).ToHandle(&result);
+  EXCEPTION_BAILOUT_CHECK(isolate, Local<Promise>());
+  return Local<Promise>::Cast(Utils::ToLocal(result));
+}
+
+
 bool v8::ArrayBuffer::IsExternal() const {
   return Utils::OpenHandle(this)->is_external();
 }